1. Field of the Invention
The present invention relates to a multi-layer ceramic capacitor having, for example, a laminated body of internal electrode patterns and ceramic layers, at end portions of which are provided external electrodes so as to connect with the internal electrodes, and in particular to a multi-layer ceramic capacitor in which de-lamination (i.e., separation between the layers) hardly occurs inside the laminated body.
2. Description of Related Art
In a multi-layer ceramic capacitor, a large number of layers are stacked or laminated, each having an internal electrode and made of dielectric material, wherein the internal electrodes face each other through the ceramic layers within this laminated body, and the above-mentioned internal electrodes extend out to the end surfaces of this laminated body. On the end portions including the end surfaces of the laminated body, to which those internal electrodes extend out, are formed external electrodes, and those external electrodes are connected to the above-mentioned internal electrodes which face each other through the ceramic layers within the laminated body.
The above-mentioned laminated body 3 of the multi-layer ceramic capacitor has a layer construction as shown in FIG. 3, for example. Namely, ceramic layers 7,7 . . . , each having an internal electrode 5 or 6 and made of a dielectric material, are laminated in the order shown in FIG. 3, and further, on both sides thereof, are stacked or laminated the ceramic layers 7, 7 . . . in a plurality thereof, on which no electrode 5 or 6 is formed. At the end portions of the laminated body 3 having such a layer structure therein, the internal electrodes 5 and 6 are exposed, and as shown in FIG. 1, the above-mentioned external electrodes 2 and 2 are formed at the end portions of this laminated body 3.
Such a multi-layer ceramic capacitor, ordinarily, is not manufactured one by one, in a unit of one part, but actually is obtained by a manufacturing method which will be described below. Namely, first of all, minute ceramic powder and organic binder are mixed to prepare a slurry, which is spread thinly on a carrier film made from a polyethylene terephthalate film, etc., by means of a doctor blade method. Then, it is dried and formed into a ceramic green sheet. Next, this ceramic green sheet is cut out into a desired size by a cutting head, while being mounted on the supporting sheet, and is printed with a conductive paste on one side surface thereof by a screen printing method, and is dried. With this, the ceramic green sheets 1a and 1b are obtained, on each of which plural sets of internal electrode patterns 2a and 2b are aligned or arranged in the vertical and horizontal directions, as shown in FIG. 6.
Next, plural pieces of the ceramic green sheets 1a and 1b, each having the above-mentioned internal electrode patterns 2a and 2b thereon, are stacked or laminated, and further stacked are several pieces of the ceramic green sheets 1, 1 . . . having no internal electrode 2a or 2b, at the top and the bottom surfaces thereof. They are compressed and form the laminated body. Here, the above ceramic green sheets 1a and 1b are stacked on one another, on which the internal electrode patterns 2a and 2b are shifted by half a length in a longitudinal direction thereof. After that, this laminated body is cut into a desired size, thereby to manufacture laminated raw chips, and those raw chips are baked. In this manner are obtained the laminated bodies shown in FIGS. 1 and 3.
Next, this baked laminated body 3 has a conductive paste applied to both ends thereof and is baked, and on the surface of the baked conductive film is provided a treated plating, thereby completing the multi-layer ceramic capacitor formed with external electrodes at both ends thereof, as shown in FIG. 1.
Within the laminated body 3 of the ceramic layers 7 in the multi-layer ceramic capacitor mentioned above, stickiness or adhesiveness between the layers of the internal electrode 5 or 6 and the ceramic layer 7 is worse than the adhesiveness between the ceramic layers 7 themselves. Therefore, when baking the laminated body 3, stresses occur inside the laminated body due to the differences in shrinkage rates and shrinking behaviors and so on, of the internal electrodes 5 and 6 and the ceramic layers 7. Then, in particular on both end portions of the laminated body 3, where the internal electrodes 5 and 6 are led out, there easily occurs a so-called de-lamination, i.e., the ceramic layers 7 peel off one another. Also, fine cracks easily occur inside the laminated body 3.
In particular, in recent years, for obtaining a larger electrostatic capacity but having a small size, the internal electrode 5 or 6 and the ceramic layer 7 have a tendency to be thin in the film thickness thereof. Therefore, with the stress due to the differences in the shrinkage rates and the shrinking behaviors of the internal electrodes 5 and 6 and the ceramic layers 7 when being baked, the laminated body 3 is under a situation that cracks and de-lamination occur more easily therein.